Among those who said they had never smoked cannabis were Gordon Brown, Justice Secretary Jack Straw, Defence Secretary Des Browne, International Development Secretary Douglas Alexander, Children, Schools and Families Secretary Ed Balls, Cabinet Office Minister Ed Miliband and Peter Hain, the Work & Pensions Secretary.

Health Secretary Alan Johnson said he "did the sex and rock and roll but not the drugs".

Hazel Blears, Secretary of State for Communities and Local Government, has said she tried the drug "once or twice when very young," according to an aide.

Those who declined to comment when contacted by the BBC included Culture Secretary James Purnell and John Denham the Innovation, Universities and Skills Secretary whose spokesman said "we don't comment on surveys".

'Personal matter'

Past cannabis use has become less of an issue for politicians in the UK over recent years as a growing number have admitted using, or trying the drug while younger.

In 2000 then shadow home secretary Ann Widdecombe's call for £100 fines for cannabis possession led to eight members of the Conservative shadow cabinet admitting to smoking cannabis in the past.

I've never taken any hard drugs. When I was a student, I took one or two puffs of marijuana but that was it.

Home Office minister Vernon Coaker last year admitted "when I was a student, I took one or two puffs of marijuana but that was it". Other past or present Labour ministers who have admitted cannabis use include Caroline Flint and Patricia Hewitt.

And on Thursday Home Office minister Tony McNulty said he had "encountered" and smoked cannabis once or twice when he was at university.

Mr Brown's official spokesman said it was a "personal matter for ministers... there is no Number 10 edict on this one way or another".

Mental health

On Wednesday, the prime minister told MPs that laws introduced in 2004, making possession of cannabis a largely non-arrestable offence, could be reversed.

In 2004 the drug was downgraded from Class B, which includes drugs like amphetamines, to Class C alongside substances like anabolic steroids, making it a largely non-arrestable offence.

Ms Smith is now to review whether it should be reversed in the light of research into links between cannabis use and mental health problems, and with crime.

A Home Office spokesman said the Advisory Council on the Misuse of Drugs (ACMD) will be asked to review reports that danger from cannabis is increasing due to wider availability of more potent strains such as "skunk".